The present invention relates to a fluorine-containing resin blend of first, and second resins. The first resin is one of an elastic fluorohydrocarbon resin and a vinylidene fluoride based resin. The second resin is mixed with the first resin for improving characteristics of the resin blend.
Fluororesins are widely used in various fields by reason of their characteristic properties attributed to the presence of C-F bond, such as good heat resistance, high resistance to oils and many other chemicals and good weather resistance. In particular, elastic fluororesins having softness and moldabililty are widely used as electrical wire covering, tubes, and composite tent materials. For example, Japanese Patent Examined Publication JP-B-62-34324 discloses an elastic fluorohydrocarbon (EFHC) resin which is superior in softness and moldability. This resin has a trunk polymer (i.e., a fluorine-containing elastic polymer) and a branch polymer (i.e., polyvinylidene fluoride). This resin can be molded under melted condition at a relatively low temperature into a tube, an electrical wire covering, a sheet, a film, and the like, with an extruder, an injection molding machine, a calender or the like.
There are proposals of resin blends each containing the EFHC resin and another resin, for improving characteristics of the resin blends as compared with the EFHC resin. For example, Japanese Patent Unexamined Publication J1P-A-62-68844 discloses a resin blend containing a first resin which is the EFHC resin having a branch polymer of vinylidene fluoride (VDF) polymer, and a second resin which is the VDF polymer or, for example, a copolymer of VDF and hexafluoroacetone (HFA). This resin is improved in mechanical strength at high temperature or water repellency. As another example, JP-A-2-135269 discloses a mixture of a first solution containing the EFHC resin dissolved in a polar solvent and a second solution containing a methyl methacrylate resin dissolved in an organic solvent. As still another example, JP-A-4-370133 discloses a resin blend containing the EFHC resin and a thermoplastic urethane resin.
Of fluororesins, VDF based resin referring to PVDF or to VDF copolymer is widely known as being resistant against corrosive chemicals and ultraviolet rays and as being superior in mechanical characteristics. VDF based resin is particularly superior in extrudability and meltability for use as a powder coating or the like. Therefore, VDF based resin is widely used as an anticorrosion coating for metal and as an electric wire coating. Furthermore, VDF has a superior characteristic as a barrier to gases, as compared with other fluororesins. For example, JP-A-4-224939 discloses a fuel distributing resin tube having an inner layer of PVDF and an outer layer of polyamide resin. PVDF is widely used in the field of paint. In particular, PVDF has been used for long as a paint for precoated metal.
PVDF is a crystalline polymer and thus is insufficient in softness. In view of this, there are proposals of resin compositions each of which contains PVDF and is improved in softness as compared with PVDF itself. For example, JP-B-55-35042 discloses a resin composition containing PVDF and a methyl acrylate resin, which is improved in softness and extensibility. As another example, JP-B-61-16769 discloses a resin composition containing the above-mentioned EFHC resin and PVDF, which is improved in impact resistance and low-temperature characteristics.